Maps and GPS directions to AT&T St. Louis MO 63131 and other AT&T Stores in the United States. Find your nearest AT&T Stores. AT&T retail stores and Device Support Centers in the United States. AT&T Inc. is the second largest provider of mobile telephone services and the largest provider of fixed telephone services, broadband subscription, television services and DirecTV in the United States. AT&T is the largest telecommunications company in the world.